Hacking the IGO Mini Powered Screwdriver for Robotics

This article details hacking the IGO Mini Screwdriver for
use in small robots. Inside the IGO is a DC motor, 5 stages
of gearing, two screwdriver bits, and 2 AAA Eveready batteries.

I found the IGO Screwdriver at Fry's in Renton (Seattle)
Washington. The package allows you to try it, and the torque
was strong for such a small package, so I immediately thought
about hacking the motor and geartrain for small robots.

The kicker for me was the price. Normal price was $5.99,
which was good, but it was on sale (12/12/2003) for $2.99.
I bought 2, used one to open up the other, and determined
that yes, it is easy to hack. I then went back and bought
10 more.

I also researched the IGO screwdriver on the web. It was
just released (December 2003) and is sold through many
drug stores or hardware stores for $6 to $10.

Here's the IGO Mini Screwdriver before hacking. It makes a nice bench-top screwdriver
but I think I'll find better use for it in robots.

Image 2. The IGO before hacking.

After playing with my new screwdriver for a while, I got serious about opening
it up...

Image 3. Backside, screw hole, and batteries.

To open the case we must:

Remove the battery-cap and the batteries. Just twist and remove.

Remove the front cap. This is the hard step, see details below.

Remove the 2 phillips screws.

Pry the case open.

Removing the front cap:

As seen in Image 4 below, the green cap is held in place by 2 tabs that fit
tightly in the 2 slots on the sides of the main case. I was able to remove the
cap by prying a small slotted screwdriver under the cap and disengaging one
tab at a time. The case and the cap are plastic, and I gouged them a bit.
You can mangle the cap since you probably don't want to put it back on.
I hacked two of these. The first one I actually cut the cap off. The second
one, knowing where the 2 tabs were, was much easier to get off.

Once the cap is off, and the 2 screws are removed, the case can be pried open.
It is a bit tight since the case is aligned using 3 metal pins along with
the plastic motor-mount.

Image 4. Backside with 2 screws and the end-cap.

Once opened, we can see that the handle is only used for the 2 AAA batteries.
The control switch is a simple double-pole double-throw switch made cheaply
on a small circuit board and held in place by the case. The switch cannot
be easily salvaged.

Image 5. An opened IGO.

Geartrain

The geartrain in the IGO Mini Screwdriver is real nice. It has 5 stages for a
reduction of 70.5.

The gear attached to the motor has 8 teeth.

The first stage has a 28-tooth gear driven by the motor, with an attached 9-tooth gear.

The second stage has a 28-tooth gear driven by the motor, with an attached 9-tooth gear.

The third stage has a 28-tooth gear driven by the motor, with an attached 12-tooth gear.
These gears are metal

The output has a 25-tooth gear attached to the end of the hex connector. This gear
and the hex connector are metal.

The hex connector also has a magnet in the end. The metal screwdriver bits
slip into the hex connector and are held in place by the magnet.

Image 6. Details of the geartrain.

Speed:

Using the 2 AAA batteries that come with the screwdriver, the output rotates
at 160 RPM. Applying 5 volts to the motor, it turns at 280 RPM. Running it
from 5 volts for over a minute did not heat up the motor. The motor can be
easily driven using your favorite technique, such as an H-bridge, DPDT relay,
or other DC-motor driving circuit. Speed can be controlled using typical PWM
control. Here are a few DC-motor control references I see in Google:

For use in a small robot, I cut the plastic case down to the minimum needed to
keep the motor and geartrain together. I used a cutoff wheel on a Dremel tool
to do the cutting. My plan is, with the notched case, to be able to place two
of these back-to-back with the notches interlocking while keeping the axels
in line with each other. This should be easy to get the wheel-to-wheel width
to less than 5 inches. For mini sumo robots as used in the Seattle Robotics
Society Robothon events, the maximum
width is 10cm (about 4 inches). With some creative cutting of the case, maybe
cutting the hex connector shorter, and possibly offsetting of the wheels,
these IGO motors and geartrains should be useful for the mini sumo robots.

Image 7. Hacked case for robot use.

Mounting:

For mounting this hacked screwdriver to a robot there are many options. I'll discuss
a few that occur to me before I actually try to mount them.

A couple of holes drilled in the case would allow me to screw the case to a base.

The 2 slots in the font could be used to mount using tabs made on the robot base.

Other simple (quick) solutions can be used, such as double-backed tape, hot glue,
zip ties, or other techniques.

Conclusion:

For $5.99 (sale price of $2.99) I got a bunch of useful items for my robotics work.
Here's a comparison based on other products at Fry's: